PSI - Issue 77

V. Kroužecký et al. / Procedia Structural Integrity 77 (2026) 161 – 169 Vít Kroužecký / Structural Integrity Procedia 00 (2026) 000 – 000

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The particle size distribution of the recycled 316L powder, shown in Figure 1 Histogram of particle size used powder, exhibits a pronounced positive skew (skewness = 3.01) and high kurtosis (15.82), indicating a long tail toward smaller particles and a sharp peak. This asymmetry reflects an increased proportion of fine particles, which is likely a consequence of repeated sieving during recycling, leading to partial separation of large and small particles. The shift toward smaller particle sizes may influence powder flowability and layer deposition in the SLM process.

Figure 1 Histogram of particle size used powder

3. Experiment To investigate the effect of process parameters on down surface quality, a design of experiment comprising twelve parameter sets was established. The laser power was varied between 100 and 250 W, while the hatch spacing ranged from 0.055 to 0.09 mm. The combinations were selected with respect to the resulting volume energy density (VED), which served as a guiding criterion for the design. In order to avoid process instabilities related to melt pool fluctuations, the VED was intentionally kept below 80 J/mm³. The calculation of VED is presented in Figure 2 Equations of volume energy density, and the complete parameter matrix is summarized in Table 3 DOE - process parameters and calculated VED for downskin samples. From the initial set of twelve parameter combinations (Table 3 DOE - process parameters and calculated VED for downskin samples), five conditions that yielded the lowest downskin surface roughness at a 35° inclination were identified (highlighted in bold). These parameter sets were subsequently selected for further evaluation at inclination angles of 30° and 25°, in order to assess their robustness with respect to down surface quality under more challenging geometrical conditions. Figure 2 Equations of volume energy density = ∗ ℎ ∗ = ቀ ቁ ∗ ∗ = 3